Text editors are often provided with operating systems or software development packages, and can be used to change programming language source code and configuration files. Configuration files, which may be referred to as config files, are used to configure the settings for some computer programs, such as user applications, server processes and operating system settings. Configuration files are often written in American Standard Code for Information Interchange (ASCII) and are often line-oriented, with lines terminated by a newline or carriage return/line feed pair, depending on the operating system. Some configuration files are created and modified using an ASCII editor, while others are created and modified as a side-effect of changing settings in a graphical user interface (GUI) program. Some applications provide tools to create, modify, and verify the syntax of their configuration files. For server processes and operating system settings, the only documentation may be the content of the file. Some configuration files are partially described by man or help pages. Some computer programs only read the configuration files at startup. Other computer programs periodically check the configuration files for changes. Some computer programs can be commanded to re-read the configuration files and apply the changes to the current process, or indeed to read arbitrary files as a configuration file.